Petal To The Kettle: What Is Kettle Souring?

Our annual Tart Series kicks off with the return of our very first kettle sour. Delicious bundles of hibiscus and rose petals combined with mouth-watering strawberry flavors, result in an appealing pinkish purple appearance. This perfect harmony of floral characteristics delivers a fruity, tart and clean finish. But this kettle sour follows a different brewing process than our sour ales at The Wood Shop production facility. Sour ales feature intense sourness from several microorganisms aging in oak barrels for up to a year or longer. These brews often include massive quantities of fruit as well. In contrast, kettle sours utilize a single bacteria, Lactobacillus, with the souring process taking place overnight to provide just the right amount of sour. To learn more about the difference between our sour and beer production, check out our blog on our award-winning gose Two of Tarts.

“Kettle sours are much less tart and complex and have more of an approachable profile,” Brewery Innovation Lead Matt Wisely said. In addition, hops aren’t a priority when making this beer. “Tartness and bitterness tend to clash, so only a minimum amount of hops are used in Petal to keep its bitterness low,” Wisely explained.

Brewing Process

But the addition of Lactobacillus is not enough to make a compelling kettle sour beer. That’s where the imaginations of our amazing brewers come into play. By adding unique ingredients that aren’t commonplace in beers, they can drastically transform a slightly tart brew. These various flavor combinations provide a truly unique experience for our fans.

Kettle sours follow all of the same steps as a typical brew with the added step of the overnight souring process. After about 16 hours, the desired level of ‘sourness’ is achieved and we have a clean, tart character in the wort. We can then boil the wort to kill off the added bacteria. Therefore allowing us to brew alongside our other beers without the fear of cross-contamination. To add rose petals and hibiscus to the mix we use a hopback, which is a small steeping vessel that infuses ingredients into hot wort. These additions provide an unmistakable fragrant floral aroma. Yeast is then added to the wort in a stainless steel fermenter to ferment for 1 to 2 weeks. Finally near the end of fermentation, strawberry puree is included to add to an already fruity profile. Consequently, these inclusions transform a slightly tart beer into an enjoyable ale.

This delicious product is a perfect example of why we began experimenting with kettle sours. Our Tart Series includes three annual releases: Petal to the Kettle (January-April), Two of Tarts (May-August), and Modern Tart (September-December).